1. Field of the Invention
The present invention relates to new water-swellable clay mineral laminated powder, dye/water-swellable clay mineral complex, and the compositions comprising the same, and in particular, relates to the impartment of functionality to the base powder and the tolerance improvement of dye in the dye/water-swellable clay mineral complex.
2. Prior Art
In the past, various laminated powders with various functionalities, which cannot be achieved by the base powder itself, have been prepared by depositing different kinds of powder particles, metal oxides, or organic compounds, etc. on the surface of the base powder. Pearlescent pigment, in which flaky mica is laminated with titanium dioxide, is a typical example of laminated powder; the pearlescent pigment expresses an interference color.
On the other hand, water-swellable clay mineral is known to form a complex with various organic compounds. Water-swellable clay mineral has a structure in which plate crystals are stacked, and cations and water molecules are sandwiched between them. Thus, a complex can be easily prepared by adsorbing molecules on the cations or by intercalating molecules by replacing the interlayer cations or water molecules. Examples of the complex with water-swellable clay mineral include a complex with a cationic molecule such as cationic dye or n-alkylamine salt; and a complex with a polar molecule such as alcohol, ketone, ether, nitrile, or water-soluble polymer. In this way, it is possible to impart various functionalities to a water-swellable clay mineral by complexing various functional molecules.
We may increase the possibility of imparting functionalities to the base powder by using, as the foundation for attaching functional molecules, the water-swellable clay mineral laminated on the surface of the base powder. However, this type of water-swellable clay mineral laminated powder has not been reported.
On the other hand, by the LbL method, which has been actively investigated in recent years, a base material with the opposite charge to that of the base material is successively adsorbed in a dilute aqueous solution or dispersion by electrostatic interaction. Thus, a multilayer laminate structure can be relatively easily constructed. In this technology, it was discovered by Iler in 1966 that colloid particles of opposite charges can be alternately and successively adsorbed (Iler: Journal of Colloid and Interface Science, 1966, 21, p. 569-594). In 1988, alternating adsorption of Zr4+ and diphosphonic acid was reported by Mallouk et al. (Mallouk et. al: Journal of American Chemical Society, 1988, 110, p. 618-620). In addition, Decher et al. reported the formation of a multilayer film of polymer electrolytes (Decher et. al: Thin Solid Films, 1994, 244, p. 772-777). These discoveries have triggered numerous reports of laminate structures of various ion species and charged colloid particles.
Kleinfeld et al. reported, in 1994, a multilayer structure in which polymer electrolyte and water-swellable clay mineral were alternately laminated on a silicon wafer substrate (Kleinfeld et al.: Science, 1994, 265, p. 370-373). Later, Lvov et al., Kotov et al., Van Duffel et al., Rouse et al., and Kim et al. reported laminates of polymer electrolyte and water-swellable clay mineral (Lvov et al.: Langmuir, 1996, 12, p. 3038-3044; Kotov et al.: Chemistry Materials, 1998, 10, p. 886-895; Van Duffel et al.: Langmuir, 1999, 15, p. 7520-7529; Rouse et al.: Chemistry Materials, 2000, 12, p. 2502-2507; and Kim et al.: Chemistry Materials, 2001, 13, p. 243-246).
However, all these multilayer structures of polymer electrolyte and water-swellable clay mineral were prepared by the immersion of a base plate (size is in the order of cm) such as a silicon wafer or mica. A material in which water-swellable clay mineral laminated on the surface of the powder as base has not been reported.
As mentioned previously, various functionalities can be imparted to water-swellable clay mineral by complexing it with various functional molecules.
On the other hand, a dye has been used in cosmetics and various coloring applications because of its clear color rendering. However, the stability such as lightfastness and chlorine resistance has often been poor. Even lake pigment in which acid dye is supported on metal has a problem in lightfastness and chlorine resistance. There is also a problem in that dye leaches out of the lake pigment. Many water-soluble dyes including acid dye and basic dye are also weak against external factors such as chlorine in water.
As an example of pigment in which dye and water-swellable clay mineral are complexed, there is a pigment in which dye is adsorbed on a complex of chitosan and swellable smectite; it is reported that this pigment has good dispersibility (Japanese Unexamined Patent Publication H03-139569). It is also reported that a complex containing dye, a linear polycation without cyclic sugar structure, and a layered clay mineral has excellent lightfastness and excellent dissolution resistance (Japanese Unexamined Patent Publication H11-116837).
In order to use chitosan in solution, however, it is necessary to use a solvent of acidic pH; thus, usable dyes are limited. The polycation used in Japanese Unexamined Patent Publication H11-116837 is an amine-type, such as polyethyleneimine, which contains a primary amino group. Therefore, it is also affected by pH. In addition, there has been a problem, in both cases, in that the content of the dye in the pigment is not sufficient, or that it is necessary to finely pulverize them to achieve sufficient color rendering. Furthermore, since the refractive index of clay mineral itself is ca. 1.5, there is a limit in the coloring abilities and hiding power of the pigment. It is also difficult to use the pigment as a substitute for an acid dye because of an in-water dispersion problem.